The present invention relates to a high-frequency signal processor and a wireless communication system. More particularly, the invention relates to a technology effectively applicable to a high-frequency signal processor having a direct conversion receiver and a wireless communication system.
As described in patent document 1; for example, the direct conversion receiver reduces secondary distortion generated in the mixer using the following circuits. One circuit supplies the mixer with a test signal having a predetermined frequency interval. Another circuit detects secondary distortion generated in the mixer. Still another circuit controls mixer parameters based on the detection result. This configuration searches for a mixer parameter to minimize the secondary distortion in the mixer. When detecting the secondary distortion in the mixer, the receiver detects an output amplitude magnitude from the mixer based on a specific frequency causing the secondary distortion.
Patent document 2 describes the technology that allows a direct conversion transmitter to reduce carrier leakage occurring in a first modulator (I-signal mixer circuit) and a second modulator (Q-signal mixer circuit). For example, carrier leakage may be reduced in the first modulator. For this purpose, the transmitter detects a phase difference between a local signal for the first modulator and an added output signal from the first modulator and the second modulator while changing a differential balance for the first modulator. The transmitter searches for a differential balance that allows the phase difference to reach a specified value (90°), namely that allows the carrier leakage to remain in only the second modulator.                Patent document 1: Japanese patent laid-open No. 2004-336822        Patent document 2: Japanese patent laid-open No. 2009-212869        